Re: [PATCH 2/7] xen/arm32: head.S: Introduce a macro to load the physical address of a symbol

[Julien Grall <julien@xxxxxxx>]

Hi Michal,

On 27/06/2022 10:59, Michal Orzel wrote:
> On 27.06.2022 11:52, Julien Grall wrote:
> > On 27/06/2022 07:31, Michal Orzel wrote:
> > > Hi Julien,
> > Hi Michal,
> >
> > > On 24.06.2022 11:11, Julien Grall wrote:
> > > > From: Julien Grall <jgrall@xxxxxxxxxx>
> > > >
> > > > A lot of places in the ARM32 assembly requires to load the physical address
> > > > of a symbol. Rather than open-coding the translation, introduce a new macro
> > > > that will load the phyiscal address of a symbol.
> > > >
> > > > Lastly, use the new macro to replace all the current open-coded version.
> > > >
> > > > Note that most of the comments associated to the code changed have been
> > > > removed because the code is now self-explanatory.
> > > >
> > > > Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
> > > > ---
> > > >    xen/arch/arm/arm32/head.S | 23 +++++++++++------------
> > > >    1 file changed, 11 insertions(+), 12 deletions(-)
> > > >
> > > > diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> > > > index c837d3054cf9..77f0a619ca51 100644
> > > > --- a/xen/arch/arm/arm32/head.S
> > > > +++ b/xen/arch/arm/arm32/head.S
> > > > @@ -65,6 +65,11 @@
> > > >            .endif
> > > >    .endm
> > > >    +.macro load_paddr rb, sym
> > > > +        ldr   \rb, =\sym
> > > > +        add   \rb, \rb, r10
> > > > +.endm
> > > > +
> > > All the macros in this file have a comment so it'd be useful to follow this 
> > > convention.
> > This is not really a convention. Most of the macros are non-trivial (e.g. they 
> > may clobber registers).
> >
> > The comment I have in mind here would be:
> >
> > "Load the physical address of \sym in \rb"
> >
> > I am fairly confident that anyone can understand from the ".macro" line... So I 
> > don't feel the comment is necessary.
> Fair enough although you did put a comment when introducing load_paddr for 
> arm64 head.S
For the better (or the worse) my way to code has evolved in the past 5 
years. :) Commenting is something that changed. I learnt from other open 
source projects that it is better to comment when it is not clear what 
the function/code is doing.
Anyway, this is easy enough for me to add if either Bertrand or Stefano 
think that it is better to add a comment.
Cheers,

--
Julien Grall